Dynamic sound attenuation at hypersonic frequencies in silica glass

In order to clarify the origin of the dominant processes responsible for the acoustic attenuation of phonons, which is a much debatted topic, we present Bril louin scattering experiments in various silica glasses of different OH impurities content. A large temperature range, from 5 to 1500 K is investigated, up to the glass transition temperature. Comparison of the hypersonic wave attenuation in various samples allows to identify two different processes. The first one induce s a low temperature peak related to relaxational processes; it is strongly sensitive to the extrinsic defects. The second, dominant in the hig h temperature range, is weakly dependent on the impurities and can be ascribed to anharmonic interactions

Applying systems-thinking to reduce check-the-box decisions in the audit of complex estimates

Even as audit regulators push for increased use of professional judgment in the audit of complex financial statement accounts, auditors seem to interpret audit standards as increasingly prescriptive. This leads to mechanical, or check-the-box audit decisions in just those situations in which it is most important to make decisions based on professional judgment. In response, regulators can, and do, issue new audit standards with a focus on providing auditors with guidelines instead of bright-lines, though those new standards often contain additional examples, definitions, and guidance which may be perceived as prescriptive. I conduct an experiment using practicing auditor participants to evaluate the joint effect of prescriptive versus judgment-based audit standards which allow auditors to use professional judgment without additional constraints, and systems- versus reductionist-thinking perspectives on auditor decisions related to complex estimates. My results indicate that introduction of a judgment-based standard is not sufficient, by itself, to decrease auditors’ check-the-box mentality. As expected, however, auditors who adopt a systems-thinking perspective are better able to apply both the prescriptive and judgment-based standards, resulting in less check-the-box decisions related to material misstatement decisions, but not to material weakness decisions. I find evidence that the systems-thinking perspective changes how auditors incorporate business process complexity into their audit planning process and changes how they perceive management’s role, relative to the role of process complexity itself, in potential accounting errors. These results suggest a potential limit to the ability to reduce auditors’ check-the-box mentality and increase their use of professional judgment by simply introducing more judgment-based standards. These results also suggest, however, that the goal of improving professional judgment may be achieved with an underlying change to the way auditors’ think, whether standards are prescriptive or more judgment-based

Birefringence and polarisation mode-dispersion in spun single-mode fibres

A theoretical and experimental analysis of the polarization properties of twisted single-mode fibers is presented. It is shown that whereas a conventionally twisted fiber possesses considerable optical rotation, a fiber which has a permanent twist imparted by spinning the preform during fiber drawing exhibits almost no polarization anisotropy. It is thus possible to virtually eliminate the commonly observed fiber linear birefringence. As a consequence, fibers made in this way are ideally suited for use in the Faraday-effect current transducer. It is further shown that a permanent twist of a few turns/meter effectively eliminates polarization mode-dispersion. The technique therefore appears attractive for enhancing the bandwidth of very long unrepeatered telecommunication links

In situ measurements of density fluctuations and compressibility in silica glass as a function of temperature and thermal history

In this paper, small-angle X-ray scattering measurements are used to determine the different compressibility contributions, as well as the isothermal compressibility, in thermal equilibrium in silica glasses having different thermal histories. Using two different methods of analysis, in the supercooled liquid and in the glassy state, we obtain respectively the temperature and fictive temperature dependences of the isotheraml compressibility. The values obtained in the glass and supercooled liquid states are very close to each other. They agree with previous determinations of the literature. The compressibility in the glass state slightly decreases with increasing fictive temperature. The relaxational part of the compressibility is also calculated and compared to previous determinations. We discussed the small differences between the different determinations

Quantum statistical effects in nano-oscillator arrays

We have theoretically predicted the density of states(DOS), the low temperature specific heat, and Brillouin scattering spectra of a large, free standing array of coupled nano-oscillators. We have found significant gaps in the DOS of 2D elastic systems, and predict the average DOS to be nearly independent of frequency over a broad band f < 50GHz. At low temperatures, the measurements probe the quantum statistics obeyed by rigid body modes of the array and, thus, could be used to verify the quantization of the associated energy levels. These states, in turn, involve center-of mass motion of large numbers of atoms, N > 1.e14, and therefore such observations would extend the domain in which quantum mechanics has been experimentally tested. We have found the required measurement capability to carry out this investigation to be within reach of current technology.Comment: 1 tex file, 3 figures, 1 bbl fil

Interferometric Techniques Using Embedded Optical Fibers for the Quantitative NDE of Composites

Optical interferometric techniques using single mode optical fiber waveguide embedded in composites and other layered materials have been used to measure one- and two-dimensional stress distributions and acoustic emission caused by applied point source loads. By interferometrically comparing the phases of coherent optical signals propagated through an embedded sample fiber and a bypass reference fiber, a signal proportional to the instantaneous strain integrated along the embedded length of the sample fiber has been detected. System calibration has been obtained by applying a one-dimensional dc strain field to a cantilever beam containing the fiber. Using this calibrated system, an array of fibers attached to a 15cm × 15cm x 0.3cm plate simply supported at the corners and subjected to point loading on the surface has been used to quantitatively determine the two-dimensional dc stress field in the plate. Finally, the calibrated ac response of the interferometer to acoustic emission events in a composite panel has been demonstrated. Potential applications are discussed

Migration scenarios and their demographic impacts for the EU member states

This deliverable both analyses the output for each migration scenario projected in Task 4.3 separately and compares different scenarios over time. At the total EU level FUME scenarios projected similar total population counts with small differences. The highest EU population in 2050 is projected by Scenario B - Recovery in Europe, stagnation in developing countries at around 518.8 million, and the lowest population is projected by No migration scenario at 387.2 million inhabitants. At national level, population sizes and compositions of the member states and the UK show more variability. Some countries are expected to experience sharp population decline at all FUME scenarios while others experience population growth. In the case of zero migration, all member states are expected to experience population decline, albeit at different paces. Migration flow composition in FUME scenarios is driven by the economical migration model presented in Deliverable 4.2 (D 4.2) and takes into account the size of diaspora and economic factors. Therefore, no surprising new origin-destination country pairs are emerging. However, when future migration flows are broken down by educational attainment the ranking of sending countries change in some cases, such as in France and Spain

Underwater Acoustic Sensors Based on Fiber Bragg Gratings

We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating) under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension and the material characteristics of the coating